Variable lordosis spacer and related methods of use

ABSTRACT

An expandable fusion device may include a first endplate and a second endplate. The expandable fusion device may also include first and second ramps configured to mate with both the first and second endplates. The first ramp may include a mating feature having a first angle relative to a vertical axis, and the second ramp may include a mating feature having a second angle relative to the vertical axis such that the first angle is different from the second angle. In particular, the first and second ramps may be configured to provide for symmetrical expansion of the first and second endplates.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.14/175,601 filed Feb. 7, 2014, the contents of which are herebyincorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

Various embodiments of the present disclosure relate generally tovariable lordosis spacers and related systems and methods. Morespecifically, the present disclosure relates to devices, systems, andmethods for correcting lordosis and/or other spinal abnormalities.

BACKGROUND

A common procedure for handling pain associated with intervertebraldiscs that have become degenerated due to various factors such as traumaor aging is the use of intervertebral fusion devices for fusing one ormore adjacent vertebral bodies. Generally, to fuse the adjacentvertebral bodies, the intervertebral disc is first partially or fullyremoved. An intervertebral fusion device is then typically insertedbetween neighboring vertebrae to maintain normal disc spacing andrestore spinal stability, thereby facilitating an intervertebral fusion.

There are a number of known conventional fusion devices andmethodologies in the art for accomplishing the intervertebral fusion.These include screw and rod arrangements, solid bone implants, andfusion devices which include a cage or other implant mechanism which,typically, is packed with bone and/or bone growth inducing substances.These devices are implanted between adjacent vertebral bodies in orderto fuse the vertebral bodies together, alleviating the associated pain.

However, there are drawbacks associated with the known conventionalfusion devices and methodologies. For example, present methods forinstalling a conventional fusion device often require that the adjacentvertebral bodies be distracted to restore a diseased disc space to itsnormal or healthy height prior to implantation of the fusion device. Inorder to maintain this height once the fusion device is inserted, thefusion device is usually dimensioned larger in height than the initialdistraction height. This difference in height can make it difficult fora surgeon to install the fusion device in the distracted intervertebralspace.

Further, lordosis refers to a curvature of the spine, and in particulara curvature that is posteriorly concave. In certain patients, thiscurvature may, for example, be larger than desired. Traditionalvertebral fusion procedures and devices do not adequately account forthis curvature. As such, traditional devices do not properly align withadjacent vertebral bodies. To ensure proper fit of traditional devices,bone may be removed from the vertebral bodies, increasing procedure andhealing time.

As such, there exists a need for a fusion device capable of beinginstalled inside an intervertebral disc space at a minimum distractionheight and for a fusion device that can maintain a normal distancebetween adjacent vertebral bodies when implanted.

SUMMARY OF THE DISCLOSURE

The present disclosure relates to embodiments of expandable fusiondevices and related methods of use.

In one aspect, the present disclosure is directed to an expandablefusion device that may include a first endplate, and a second endplate.The expandable fusion device also may include a first ramp configured tomate with both the first and second endplates. The first ramp may be awedge with an incline extending along a longitudinal axis of theexpandable fusion device, and also may be a wedge having an inclineextending along a lateral axis of the expandable fusion device. A secondramp may be configured to mate with both the first and second endplates.The second ramp may be a wedge having an incline extending along thelongitudinal axis of the expandable fusion device, and also may be wedgehaving an incline extending along the lateral axis of the expandablefusion device.

Various examples of the present disclosure may include one or more ofthe following aspects: wherein the first and second endplates may eachinclude at least one first mating feature configured to mate with atleast one corresponding first mating feature disposed on the first ramp;wherein the at least one mating feature of the first and secondendplates may be slidable with respect to the corresponding first matingfeature disposed on the first ramp; wherein the first and secondendplates may each include a second mating feature configured to matewith a corresponding second mating feature disposed on the first ramp;wherein the second mating feature and the corresponding second matingfeature may each be C-shaped, V-shaped, or U-shaped; wherein the firstand second endplates may each include a third mating feature configuredto mate with a corresponding third mating feature disposed on the secondramp; wherein the third mating feature and the corresponding thirdmating feature may each be C-shaped, V-shaped, or U-shaped; wherein eachof the first and second endplates may have an inner surface configuredto mate with the first ramp, wherein the inner surface of each of thefirst and second endplates may be shaped as a concave curve, the concavecurve being formed about a longitudinal axis of the expandable fusiondevice; wherein the expandable fusion device may be movable between acollapsed configuration and an expanded configuration; wherein the firstramp may be coupled to the second ramp by an actuating mechanism, andthe expandable fusion device may be configured to transition from thecollapsed configuration to the expanded configuration via actuation ofthe actuating mechanism to move the second ramp and the first ramptoward one another; wherein, in the expanded configuration, theexpandable fusion device may he a wedge having an incline extendingalong the lateral axis of the expandable fusion device; and wherein thefirst and second endplates each may have an outer surface configured tocontact a respective vertebral body, wherein each outer surface of thefirst and second endplates may have one or more of teeth, ridges,friction increasing elements, keels, or gripping or purchasingprojections.

In another aspect, the present disclosure may be directed to anexpandable fusion device. The expandable fusion device may include afirst endplate and a second endplate, and both the first and secondendplates may extend from a first side of the expandable fusion deviceto a second side of the expandable fusion device. The expandable fusiondevice also may include a first ramp and a second ramp. Both the firstramp and the second ramp may be configured to mate with both the firstand second endplates, and both the first ramp and the second ramp mayextend from the first side of the expandable fusion device to the secondside of the expandable fusion device. At least one of the first andsecond sides of the expandable fusion device may pivotally expand abouta pivot point.

Various examples of the present disclosure may include one or more ofthe following aspects: wherein both of the first and second sides of theexpandable fusion device may pivotally expand about the same pivotpoint; wherein the same pivot point may be a point disposed outside ofthe expandable fusion device; wherein the pivot point may be disposedalong the first side or between the first and second sides of theexpandable fusion device; and wherein only the second side of theexpandable fusion device may pivot about the pivot point.

In yet another aspect, the present disclosure may be directed to anexpandable fusion device. The expandable fusion device may include afirst endplate and a second endplate, and both the first and secondendplates may extend from a first side of the expandable fusion deviceto a second side of the expandable fusion device. The expandable fusiondevice also may include a first ramp and a second ramp, and both thefirst ramp and the second ramp may be configured to mate with both thefirst and second endplates, and both the first ramp and the second rampmay extend from the first side of the expandable fusion device to thesecond side of the expandable fusion device. The first and second sideof the expandable fusion device may form concentric arcs about a pivotpoint.

Various examples of the present disclosure may include one or more ofthe following aspects: wherein the expandable fusion device may bemovable between a collapsed configuration and an expanded configuration,and both of the first and second sides of the expandable fusion devicemay have same angular rate of change when moving between the collapsedconfiguration and the expanded configuration; and wherein the first sideof the expandable fusion device may be defined by a first radius, thesecond side of the expandable fusion device may be defined by a secondradius, and the first radius may be smaller than the second radius.

In yet another aspect, the present disclosure may be directed to anexpandable fusion device having a first endplate and a second endplate.The first and second endplates may each include at least one matingfeature. A first ramp may be configured to mate with both the first andsecond endplates, and the first ramp may include a mating feature havinga first angle relative to a vertical axis. The mating feature of thefirst endplate and/or second endplate is slidable with respect to thecorresponding mating feature disposed on the first ramp. A second rampmay he configured to mate with both the first and second endplates, andthe second ramp may include a mating feature having a second anglerelative to the vertical axis. The first angle may be the same ordifferent from the second angle. If different, the first angle may belarger or smaller than the second angle. It may be preferred that thesecond angle is smaller than the first angle.

Various examples of the present disclosure may include one or more ofthe following aspects: wherein the first angle is greater than thesecond angle; wherein the first angle is about 50-70°; wherein the firstangle is about 60°; wherein the second angle is about 5-25°; wherein thesecond angle is about 15°; wherein the first and second ramps areconfigured to provide for symmetrical expansion of the first and secondendplates; wherein at least a portion of the first ramp includes acurved ramp surface; and wherein at least a portion of the first ramphas a continuously changing ramp angle.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various exemplary embodiments andtogether with the description, serve to explain the principles of thedisclosed embodiments.

FIG. 1 is a side view of an embodiment of an expandable fusion deviceshown between adjacent lordotic vertebrae according to the presentdisclosure.

FIG. 2 is a longitudinal side view of an embodiment of an expandablefusion device in a first configuration according to the presentdisclosure.

FIG. 3 is a lateral side view of the expandable fusion device of FIG. 2.

FIG. 4 is a cross-sectional view of the expandable fusion device of FIG.2 taken along line 4-4.

FIG. 5 depicts the expandable fusion device of FIG. 2 in a secondconfiguration.

FIG. 6 is a lateral side view of the expandable fusion device of FIG. 5.

FIG. 7 is a cross-sectional view of the expandable fusion device of FIG.5 taken along line 7-7.

FIG. 8 is a side view of the expandable fusion device of FIG. 2 in thefirst configuration, showing a pivot point.

FIG. 9 is a side view of the expandable fusion device of FIG. 2 in thesecond configuration, showing the pivot point of FIG. 8.

FIG. 10 is a perspective view of the expandable fusion device of FIG. 2.

FIG. 11 is an exploded view of the expandable fusion device of FIG. 2.

FIG. 12 is another exploded view of the expandable fusion device of FIG.2.

FIG. 13 is a lateral side view of an endplate incorporated into theexpandable fusion device of FIG. 12.

FIG. 14 is a top view of the endplate of FIG. 13.

FIG. 15 is a longitudinal side view of the endplate of FIG. 13.

FIG. 16 is a perspective view of a first ramp incorporated into theexpandable fusion device of FIG. 12.

FIG. 17 is a lateral side view of the first ramp of FIG. 16.

FIG. 18 is a lateral side view of a second ramp incorporated into theexpandable fusion device of FIG. 12.

FIG. 19 is a cross-sectional an expandable fusion device according toanother embodiment of the present disclosure.

FIG. 20 is an exploded view of an expandable fusion device according toanother embodiment of the present disclosure.

FIG. 21 is a perspective view of the expandable fusion device shown inFIG. 20.

FIG. 22 is a side view of the expandable fusion device shown in FIG. 20and depicting different rates of expansion between the front and back ofthe implant.

FIG. 23 shows a cross sectional view of the expandable fusion deviceshown in FIG. 20 including the ramp angles.

FIG. 24 is a side view of the expandable fusion device shown in FIG. 20and depicting the ramp angle.

FIG. 25 is a front view of the front, first ramp which may be used withany of the expandable fusion devices described herein.

FIG. 26 is a top view of the first ramp shown in FIG. 25.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

A spinal fusion is typically employed to eliminate pain caused by themotion of degenerated disk material. Upon successful fusion, a fusiondevice becomes permanently fixed within the intervertebral disc space.Referring to FIG. 1, an expandable fusion device 10 is shown betweenadjacent vertebral bodies 2 and 3. Expandable fusion device 10 mayextend from a first side 22 (e.g., a posterior side) to a second side 24(e.g., an anterior side). Expandable fusion device 10 may engage theendplates of adjacent vertebral bodies 2 and 3 and, in an installedposition, maintain normal intervertebral disc spacing and restore spinalstability, thereby facilitating an intervertebral fusion. In someembodiments, expandable fusion device 10 may provide indirectdecompression (e.g., by reducing the pressure of vertebral bodies 2 and3 on adjacent nerves) while still providing lordosis correction.Expandable fusion device 10 may be formed from any suitable material orcombination of materials, including, but not limited to, titanium,stainless steel, titanium alloys, non-titanium metallic alloys,polymeric materials, plastics, plastic composites, polyetheretherketone(PEEK), ceramic, and elastic materials, among others.

In an embodiment, the expandable fusion device 10 may be configured andsized to be placed down an insertion tube and into the disc spacebetween the adjacent vertebral bodies 2 and 3. For example, expandablefusion device 10 may he configured for insertion through an insertiontube, such as, e.g., a cannula. It should be noted, however, that theinsertion tube may alternatively have any suitable diameter. In oneembodiment, expandable fusion device 10 may be inserted through acannula having a diameter of about 8.5 mm. In some embodiments, theexpandable fusion device 10 may have a width in a range of from about 8mm to about 26 mm, and a length in a range from about 20 mm to about 65mm, or may have other suitable dimensions. Expandable fusion device 10may be inserted into a patient via a direct lateral procedure, althoughanterior, anterolateral, posterolateral or posterior proceduresalternatively may be utilized.

Expandable fusion device 10 may be generally wedge shaped, and may havea height that increases from first side 22 toward second side 24. Insome embodiments, the expandable fusion device 10 may be expanded to aheight that is equal to or greater than about 150% of its initialheight. In one embodiment, the expandable fusion device 10 may beexpanded to a height that is equal to or greater than about 200% of itsinitial height, or another suitable percentage of its initial height.

As shown in FIG. 10, expandable fusion device 10 may include one or moreopenings 26 to accommodate bone growth along the longitudinal length ofthe expandable fusion device 10. In some embodiments, openings 26 mayhave the same dimensions, or may alternatively have differentdimensions. In the embodiment shown, expandable fusion device 10 has twoopenings 26, although other suitable numbers and dimensions of openingsare also contemplated. Openings 26 may be sufficiently large tofacilitate bone growth after installation of expandable fusion device 10between vertebral bodies 2 and 3.

In an exemplary embodiment, bone graft or similar bone growth inducingmaterial may be introduced around and within the expandable fusiondevice 10 to further promote and facilitate the intervertebral fusion.The expandable fusion device 10, in one embodiment, may be packed withbone graft (e.g., autograft or allograft) or similar bone growthinducing material to promote the growth of bone through and around theexpandable fusion device 10. The bone graft may be packed between theendplates of the adjacent vertebral bodies prior to, subsequent to, orduring implantation of the fusion device.

In one embodiment, expandable fusion device 10 may be treated with atitanium and/or hydroxyapatite plasma spray coating to encourage bonyon-growth, improving the strength and stability of the connectionbetween the respective component and the underlying bone (e.g., avertebral body). Any other suitable coating also may be provided onexpandable fusion device 10. Such coatings may include therapeuticagents, if desired. Expandable fusion device 10 also may includeradiopaque markings to facilitate in vivo visualization. In someembodiments, portions of expandable fusion device 10 may be formed of aradiolucent material, while other portions of expandable fusion device10 may be formed of radiopaque materials to facilitate imaging of theradiopaque portions of expandable fusion device 10, such as, e.g.,actuating mechanisms, endplates, ramps, or the like.

With reference to FIGS. 2-12, an embodiment of the expandable fusiondevice 10 is shown. In an exemplary embodiment, the expandable fusiondevice 10 may include a first endplate 14, a second endplate 16, a firstramp 18, and a second ramp 20. Expandable fusion device 10 may bemovable between a collapsed configuration shown in FIGS. 2-4 and 8, andan expanded configuration shown in FIGS. 5-7 and 9. The ability ofexpandable fusion device 10 to reciprocally move between the collapsedand expanded configurations may provide numerous benefits. For example,because expandable fusion device 10 can be inserted between thevertebral bodies 2 and 3 in a collapsed configuration that is smallerthan the expanded configuration, the large impaction forces needed toinstall traditional fusion devices are not required to installexpandable fusion device 10. In one embodiment, expandable fusion device10 may be in a lordotic state in the collapsed configuration, althoughother suitable configurations, such as, e.g., parallel or other startingangles, are also contemplated.

Expandable fusion device 10 may expand and collapse about a set pivotpoint P, shown in FIGS. 8 and 9. Expandable fusion device 10 may beconstructed to alter the position of pivot point P. That is, first ramp18, second ramp 20, and endplates 14, 16 may be constructed to exhibit acurvature (e.g., may have a radius of curvature) about pivot point P, asfurther described below. In the collapsed configuration shown in FIGS.2-4 and 8, expandable fusion device 10 may maintain an angle α (shownonly in FIG. 8) with respect to pivot point P. In the expandedconfiguration shown in FIGS. 5-7 and 9, expandable fusion device 10 maymaintain an angle β (shown only in FIG. 9) with respect to pivot pointP. The construction of expandable fusion device 10 also may select therate of change between angles α and β in the transition of expandablefusion device 10 between the collapsed and expanded configurations. Insome embodiments, expandable fusion device 10 may experience a linearincrease in the lordotic angle during the transition from the collapsedconfiguration to the expanded configuration through an expansion range).In some embodiments, expandable fusion device 10 may be constructed toset pivot point P closer to the expandable fusion device 10 (or evenwithin the perimeter of expandable fusion device 10). As pivot point Pmoves toward expandable fusion device 10 (or further toward a midline204 shown in FIGS. 8 and 9), the rate of angle change per height changeexhibited by expandable fusion device 10 may increase. Because secondside 24 has a larger distance from pivot point P than first side 22,second side 24 may increase in height faster than first side 22 in thetransition of expandable fusion device 10 from the collapsedconfiguration to the expanded configuration. Thus, expandable fusiondevice 10 may be constructed in various configurations to set differentα and β angles (i.e., different ramp angles on the anterior andposterior sides of expandable fusion device 10).

The position of pivot point P may be dependent or independent upon theinclination of expandable fusion device 10 between first side 22 andsecond side 24. That is, as the difference in height between first side22 and second side 24 increases, pivot point P may be set closer toexpandable fusion device 10, or even within the perimeter of expandablefusion device 10. Thus, as pivot point P is set closer to expandablefusion device 10 (or further toward midline 204), angles α and β maybecome larger. On the contrary, as the pivot point P is set further fromexpandable fusion device 10, a smaller rate of angle change per heightchange, and smaller α and β angles will be present in expandable fusiondevice 10.

In one embodiment, α may be about 10.4°, β may be about 22.5°, and adistance d between pivot point P and first side 22, may be about 17 mmalthough other suitable values are also contemplated.

First and second sides 22, 24 or expandable fission device 10 may thusbe formed as arcs (e.g., concentric arcs) about pivot point P. In thecollapsed configuration, first side 22 may be oriented at angle α withrespect to pivot point P, and may have a radius r_(pc). In the collapsedconfiguration, second side 24 also may be oriented at angle α withrespect to pivot point P, but may have a radius r_(ac) that is largerthan radius r_(pc), as second side 24 may be oriented at a furtherdistance from pivot point P than first side 22. In the expandedconfiguration, first and second sides 22, 24 of expandable fusion device10 may expand at a substantially similar angular rate, and may bothbecome oriented at angle β with respect to pivot point P. In theexpanded configuration, first side 22 may have a radius r_(pc) that isconstant with radius r_(pc).

The curvatures of first ramp 18, second ramp 20, and endplates 14, 16,may determine the location of pivot point P. As shown in FIGS. 8 and 9,the curvatures of first ramp 18, second ramp 20, and endplates 14, 16may cause first and second sides 22, 24 of expandable fusion device 10to be curved about pivot point P to form portions of the aforementionedconcentric arcs. The curvature of first and second sides 22, 24, may setthe distance of pivot point P from first and second sides 22, 24. Thatis, if expandable fusion device 10 is constructed so as to positionpivot point P relatively farther from first and second sides 22, 24,each of first and second sides 22, 24 may have shallower curvatures. Onthe contrary, if expandable fusion device 10 is constructed so as toposition pivot point P relatively closer to first and second sides 22,24 (or even between first and second sides 22, 24), each of first andsecond sides 22, 24 may have steeper curvature.

Referring to FIGS. 11 and 12, endplates 14, 16 may have a first end 30and a second end 32. In the illustrated embodiment, the endplates 14, 16may include an outer surface 40 connecting the first end 30 and thesecond end 32, and an inner surface 42 connecting the first end 30 andthe second end 32. Outer surface 40 and inner surface 42 may both bedefined by first and second ends 30, 32, and by a first side 44 and asecond side 45. First side 44 of endplates 14, 16 may be disposed atfirst side 22 of expandable fusion device 10. Similarly, second side 45of endplates 14, 16 may be disposed at second side 24 of expandablefusion device 10. First and second sides 44, 45 may define a pluralityof mating features configured to engage with one or more mating featuresof first ramp 18 and second ramp 20. In one embodiment, both first andsecond sides 44, 45 may extend from inner surface 42. Second side 45 mayextend further from inner surface 42 than first side 44.

First side 44 may include a mating feature 46 at first end 30, at leastone mating feature 47 at an intermediate portion, and a mating feature48 at second end 32.

Mating feature 46 may be substantially C-shaped, V-shaped, U-shaped, orotherwise suitably shaped. In the embodiment shown, mating feature 46may form a slidable joint with a corresponding mating feature (e.g., oneof mating features 77 or 146 described in further detail below). Theslidable joint may be, e.g., a tabled splice joint, or another suitablejoint. That is, mating feature 46 and its corresponding mating feature77 or 146 may be similarly shaped to have a groove disposed between twoshoulders. One shoulder of mating feature 46 may slide within the grooveof the corresponding mating feature 77 or 146, while one shoulder of thecorresponding mating feature 77 or 146 may slide within the groove ofmating feature 46. In some embodiments, It should be understood thatmating feature 46 and its corresponding mating feature 77 or 146 may beformed in any other suitable manner. For example, mating feature 46 andits corresponding mating feature 77 or 146 may form another splicejoint, a tongue and groove joint, another suitable joint, or be relatedto each other in another suitable manner. In some embodiments, matingfeature 46 and its corresponding mating feature 77 or 146 may beslidable and/or interlocking with one another. In some embodiments,mating feature 46 may be inclined along longitudinal axis 200 from firstend 30 of endplates 14, 16 toward an intermediate portion of endplates14, 16.

In the embodiment shown by FIGS. 11 and 12, mating features 47 are shownas defining inwardly facing recesses or grooves. The recesses of matingfeatures 47 may accept a protrusion or tongue of a corresponding matingfeature (e.g., mating features 84 and 86 described in further detailbelow). Thus, mating features 47 and its corresponding mating features84 or 86 may form a tongue and groove joint. That is, the tongue of thecorresponding mating feature 84 or 86 may be slidable within the grooveof mating feature 47. It is also contemplated that mating feature 47 andits corresponding mating feature 84 or 86 may form another type ofjoint, such as, e.g., a splice joint, another suitable joint, or berelated to each other in another suitable manner. In some embodiments,mating features 47 and their corresponding mating features 84 or 86 maybe slidably interlocking with one another. In some embodiments, matingfeatures 47 may be inclined along longitudinal axis 200 from arespective intermediate portion of endplates 14, 16 toward first end 30of endplates 14, 16. Thus, the inclinations of mating feature 46 andmating features 47 may generally oppose one another. Alternatively,mating features 47 may be inclined in any other suitable direction, suchas, e.g., from a respective intermediate portion of endplates 14, 16toward second end 32 of endplates 14, 16.

Mating feature 48 and its corresponding mating feature (e.g., matingfeatures 78 and 148 described in further detail below) may besubstantially similar to mating feature 46 described above. In someembodiments, mating feature 48 may be inclined along longitudinal axis200 from second end 32 of endplates 14, 16 toward an intermediateportion of endplates 14, 16. Thus, the inclinations of mating features46 and 48 may oppose one another, but the inclinations of matingfeatures 47 and 48 may be generally aligned (e.g., substantiallyparallel).

Second side 45 may include a mating feature 49 at first end 30, at leastone mating feature 50 at an inner (or intermediate) portion, and amating feature 51 at second end 32. Mating feature 49 may be similar tomating feature 46 described above, except that mating feature 49 mayhave different (e.g., larger) dimensions than mating feature 46. Similarto mating feature 46, mating feature 49 may be inclined alonglongitudinal axis 200 from first end 30 of endplates 14, 16 toward anintermediate portion of endplates 14, 16.

Mating features 50 may be similar to mating features 47, except thatmating features 50 may have different (e.g., larger) dimensions thanmating features 47. Similar to mating features 47, mating features 50may be inclined along longitudinal axis 200 from a respectiveintermediate portion of endplates 14, 16 toward first end 30 ofendplates 14, 16. Thus, the inclinations of mating feature 49 and matingfeatures 50 may generally oppose one another. Alternatively, matingfeatures 50 may be inclined in any other suitable direction, such as,e.g., from a respective intermediate portion of endplates 14, 16 towardsecond end 32 of endplates 14, 16.

Mating feature 51 may be substantially similar to mating feature 46described above. However, in some embodiments, mating feature 51 mayhave different (e.g., larger) dimensions than mating feature 46. Similarto mating feature 46, mating feature 51 may be inclined along alongitudinal axis 200 (referring to FIG. 10) from second end 32 ofendplates 14, 16 toward an intermediate portion of endplates 14, 16.Thus, the inclinations of mating features 46 and 48 may oppose oneanother, but the inclinations of mating features 50 and 51 may begenerally aligned (e.g., substantially parallel).

Mating features 46-51 may be configured to mate with a correspondingmating feature on one of first and second ramps 18 and 20 in a slidableand/or interlocking relationship.

Outer surface 40 and/or inner surface 42 may be curved about one or moreaxes. For example, outer surface 40 and/or inner surface 42 may becurved about longitudinal axis 200. Thus, in one embodiment, outersurface 40 may be convex, while inner surface 42 may be concave aboutthe longitudinal axis 200. In some embodiments, material can be added toor removed from outer surface 40 to modify the interaction between outersurface 40 and vertebral bodies 2 and 3. For example, material can beadded to give outer surface 40 a generally flat configuration whilemaintaining the concavity of inner surface 42.

The respective mating features of endplates 14, 16 may be curved inorder to impart a curvature to first and second sides 22, 24 ofassembled expandable fusion device 10 as set forth above. As best seenin FIG. 13, first and second sides 44 and 45 may be curved (e.g., mayhave a radius of curvature) about pivot point P, and thus matingfeatures 46-51 that are disposed in one of first and second sides 44, 45may be similarly curved with respect to pivot point P.

In some embodiments, the outer surface 40 of endplates 14, 16 may beflat and generally planar to allow the outer surface 40 engage with anadjacent vertebral body. Alternatively, the outer surface 40 may becurved convexly or concavely to allow for a greater or lesser degree ofengagement with the adjacent vertebral body. It is also contemplatedthat the outer surface 40 may be generally planar but include agenerally straight ramped surface or a curved ramped surface. The rampedsurface may allow for engagement with the adjacent vertebral body in afurther lordotic fashion. In one embodiment, the outer surface 40 mayinclude texturing to aid in gripping the adjacent vertebral bodies.Although not limited to the following, the texturing may include teeth,ridges, friction increasing elements, keels, or gripping or purchasingprojections.

Referring now to FIGS. 11, 12, and 16, the first ramp 18 may have afirst end 70, a second end 72, a first side portion 74 connecting thefirst end 70 and the second end 72, and a second side portion 76 on theopposing side of the first ramp 18 connecting the first end 70 and thesecond end 72. The first ramp 18 may further include a third end (e.g.,an upper end) 28, which is sized to receive at least a portion of thefirst endplate 14, and an fourth end (e.g., a lower end) 29, which issized to receive at least a portion of the second endplate 16.

The first end 70 of the first ramp 18, in an exemplary embodiment, mayinclude four mating features 77, 78, 80, and 82 (mating feature 82 shownonly in FIG. 16). Each of mating features 77, 78, 80, 82 may be shapedto mate with a respective mating feature disposed on one of endplates14, 16. Mating feature 77 may be configured to mate with, and may besimilarly shaped as mating feature 46 of endplate 14. Mating feature 78may be configured to mate with, and may be similarly shaped as matingfeature 48 of endplate 16. Mating feature 80 may be configured to matewith, and may be similarly shaped as mating feature 49 of endplate 14.Mating feature 82 may be configured to mate with, and may be similarlyshaped as mating feature 51 of endplate 16. Each of mating features 77,78, 80, and 82 may have substantially similar inclinations (with respectto an assembled expandable fusion device 10) their respective andcorresponding mating features set forth above. In one embodiment, eachof mating features 77, 78, 80, and 82 are inclined from an intermediateportion of first ramp 18 toward first end 70 of first ramp 18, althoughother suitable configurations are also contemplated. In one embodiment,mating features 77 and 78 extend from third end 28, while matingfeatures 78 and 82 extend from fourth end 29.

First side portion 74 may include mating features 84 and 86 that areconfigured to mate with various mating features of endplates 14, 16.

Mating features 84 may be protrusions extending from an intermediateportion of first side portion 74 toward first end 70. In one embodiment,mating features 84 may have a surface that is inclined from theintermediate portion of first side portion 74 toward first end 70. Theinclined surface of mating features 84 also may extend laterally outwardfrom first side portion 74. Mating features 84 also may extend fromthird end 28 of first ramp 18. The inclined surface of mating features84 may extend toward a generally flattened surface that is substantiallyparallel to longitudinal axis 200 of expandable fusion device 10. In oneembodiment, first ramp 18 may include at least two mating features 84that are staggered along first side portion 74, although other suitablenumbers of mating features 84 may alternatively be utilized. In theembodiment shown, mating features 84 are substantially similar to oneanother, although it is contemplated that mating features 84 may bedifferent than one another. Mating features 84 may be configured to matewith mating features 47 of endplate 14. In the embodiment shown in FIGS.11 and 12, mating features 47 and 84 may form a slidable andinterlocking (e.g., a tongue and groove) joint that allows expandablefusion device 10 to move between the collapsed and expandedconfigurations. However, it is contemplated that mating features 47 and84 may be modified to other suitable configurations that allowexpandable fusion device 10 to move between the collapsed and expandedconfigurations. For example, in one alternative embodiment, matingfeatures 47 may be formed as protrusions, while mating features 84 areformed as recesses. In another alternative embodiment, each of matingfeatures 47 and 84 may be formed as grooves disposed between twoshoulders such that mating features 47 and 84 form a splice joint (e.g.,similar to the tabled splice joints described above)

Mating features 86 may be protrusions extending from an intermediateportion of first side portion 74 toward first end 70. In one embodiment,mating features 86 may have a surface that is inclined from theintermediate portion of first side portion 74 toward first end 70. Theinclined surface of mating features 86 also may extend laterally outwardfrom first side portion 74. Unlike mating features 84, mating features86 may extend from fourth end 29 of first ramp 18. Thus, mating features84 and 86 may extend in generally opposite vertical directions fromfirst side portion 74. The inclined surface of mating features 86 mayextend toward a generally flattened surface that is substantiallyparallel to longitudinal axis 200 of expandable fusion device 10. In oneembodiment, first ramp 18 may include at least two mating features 86that are staggered along first side portion 74, although other suitablenumbers of mating features 86 may alternatively be utilized. In someembodiments, each of mating features 84 and 86 may be staggered from oneanother, although other suitable configurations are also contemplated.In the embodiment shown, mating features 86 are substantially similar toone another, although it is contemplated that mating features 86 may bedifferent than one another. Mating features 86 may be configured to matewith mating features 47 of endplate 16. In the embodiment shown in FIGS.11 and 12, mating features 47 and 86 may form a slidable andinterlocking (.g., a tongue and groove) joint that allows expandablefusion device 10 to move between the collapsed and expandedconfigurations. However, it is contemplated that mating features 47 and86 may be modified to other suitable configurations that allowexpandable fusion device 10 to move between the collapsed and expandedconfigurations (e.g., in a substantially similar manner as describedabove with reference to mating features 47 and 84).

Second side portion 76 may include mating features 88 and 90 that areconfigured to mate with various mating features of endplates 14, 16.

Mating features 88 may be protrusions extending from an intermediateportion of second side portion 76 toward first end 70. In oneembodiment, mating features 88 may have a surface that is inclined fromthe intermediate portion of second side portion 76 toward first end 70.The inclined surface of mating features 88 also may extend laterallyoutward from second side portion 76. Mating features 88 also may extendfrom third end 28 of first ramp 18. The inclined surface of matingfeatures 88 may extend toward a generally flattened surface that issubstantially parallel to longitudinal axis 200 of expandable fusiondevice 10. In one embodiment, first ramp 18 may include at least twomating features 88 that are staggered along second side portion 76,although other suitable numbers of mating features 88 may alternativelybe utilized. In the embodiment shown, mating features 88 aresubstantially similar to one another, although it is contemplated thatmating features 88 may be different than one another. Mating features 88may be configured to mate with mating features 50 of endplate 14. In theembodiment shown in FIGS. 11 and 12, mating features 50 and 88 may forma slidable and interlocking (e.g., a tongue and groove) joint thatallows expandable fusion device 10 to move between the collapsed andexpanded configurations. However, it is contemplated that matingfeatures 50 and 88 may be modified to other suitable configurations thatallow expandable fusion device 10 to move between the collapsed andexpanded configurations (e.g., in a substantially similar manner asdescribed above with reference to mating features 47 and 84).

Mating features 90 may be protrusions extending from an intermediateportion of second side portion 76 toward first end 70. In oneembodiment, mating features 90 may have a surface that is inclined fromthe intermediate portion of second side portion 76 toward first end 70.The inclined surface of mating features 90 also may extend laterallyoutward from second side portion 76. Unlike mating features 88, matingfeatures 90 may extend from fourth end 29 of first ramp 18. Thus, matingfeatures 88 and 90 may extend in generally opposite vertical directionsfrom second side portion 76. The inclined surface of mating features 90may extend toward a generally flattened surface that is substantiallyparallel to longitudinal axis 200 of expandable fusion device 10. In oneembodiment, first ramp 18 may include at least two mating features 90that are staggered along second side portion 76, although other suitablenumbers of mating features 90 may alternatively be utilized. In someembodiments, each of mating features 88 and 90 may be staggered from oneanother, although other suitable configurations are also contemplated.In the embodiment shown, mating features 90 are substantially similar toone another, although it is contemplated that mating features 90 may bedifferent than one another. Mating features 90 may be configured to matewith mating features 50 of endplate 16. In the embodiment shown in FIGS.11 and 12, mating features 50 and 90 may form a slidable andinterlocking (e.g., a tongue and groove) joint that allows expandablefusion device 10 to move between the collapsed and expandedconfigurations. However, it is contemplated that mating features 50 and90 may be modified to other suitable configurations that allowexpandable fusion device 10 to move between the collapsed and expandedconfigurations (e.g., in a substantially similar manner as describedabove with reference to mating features 47 and 84).

The respective mating features of first ramp 18 may be curved in orderto impart the curvature to first and second sides 22, 24 of assembledexpandable fusion device 10 as set forth above. That is, the matingfeatures of first ramp 18 may have a radius of curvature about pivotpoint P. Further, as the mating features of first ramp 18 may becomplimentary to corresponding mating features along endplates 14, 16,the mating features of endplates 14, 16 also may have a radius ofcurvature about pivot point P. Referring to FIG. 17, mating features 77,78, 80, 82, 84, 86, 88, and 90 may each have a radius of curvature aboutpivot point P. Thus, all or a portion of first ramp 18 may be bent aboutpivot point P. The geometry of first ramp 18 (e.g., any of theaforementioned radii of curvature) may be approximated with simplerfeatures for manufacturing ease.

As shown in FIG. 11, first ramp 18 may include both a bore 418 and abore 515. In some embodiments, the bore 418 may be threaded andconfigured to receive a threaded member 302 of an actuating mechanism300. The central longitudinal axis of the bore 418 may be off-centerfrom the central longitudinal axis of the first ramp 18 in order toaccommodate the bore 515.

The adjacent bore 515 may serve as an access port to allow graftmaterial to be delivered through the first ramp 18, either prior toinsertion or even in situ, if desired. The bore 418 may align with abore 366 in second ramp 20 and bore 515 may align with an additionalbore 512 in the second ramp 20, as discussed below.

Second ramp 20 may be disposed adjacent to first ramp 18 in expandablefusion device 10. Second ramp 20 may include four mating features 146,148, 149, and 151. Each of mating features 146, 148, 149, and 151 may besubstantially similar to mating feature 46 described above, and may beconfigured to mate with a respective mating feature disposed on one ofendplates 14, 16. Mating feature 146 may be configured to mate withmating feature 46 of endplate 16. Mating feature 148 may be configuredto mate with mating feature 48 of endplate 14. Mating feature 149 may beconfigured to mate with mating feature 49 of endplate 16. Mating feature151 may be configured to mate with mating feature 51 of endplate 14.

The respective mating features of second ramp 20 may be curved in orderto impart the curvature to first and second sides 22, 24 of assembledexpandable fusion device 10 as set forth above. Further, as the matingfeatures of second ramp 20 may have a radius of curvature about pivotpoint P, the mating features of endplates 14, 16 also may have a radiusof curvature about pivot point P. Mating features 146, 148, 149, and 151may be all curved about pivot point P. Thus, all or a portion of secondramp 20 may he bent about pivot point P. The geometry of second ramp 20(e.g., any of the aforementioned radii of curvature) may be approximatedwith simpler features for manufacturing ease.

In one alternative embodiment, expandable fusion device 10 may be formedso as to locate pivot point P within lateral width of the expandablefusion device 10 along first side 22 of expandable fusion device 10. Inthis alternative embodiment, all mating features (e.g., tracks,protrusions, grooves, shoulders, and the like) disposed along first side22 of expandable fusion device 10 (e.g., along endplates 14, 16, andfirst and second ramps 18 and 20) may be replaced by linkage or pivotingmechanisms. When pivot point P is located within lateral width of theexpandable fusion device 10 along first side 22 of expandable fusiondevice 10, only second side 24 may pivot about pivot point P duringexpansion and collapse of expandable fusion device 10.

As described above, the second ramp 20 may include a bore 366 adjacentbore 512. The bore 366 may be configured to receive an actuatingmechanism 300 therethrough, and may be aligned with the bore 418 in thefirst ramp 18. Accordingly, the bore 366 may have a central longitudinalaxis that is off-set from the central longitudinal axis of the secondramp 20 to accommodate the adjacent bore 512. The bore 512 of the secondramp 20 may be aligned with the bore 515 of the first ramp 18 to allowgraft material to be inserted into the implant, either prior to or evenafter insertion of the implant.

First and second ramps 18 and 20 may each be a wedge having an inclineextending in at least two planes. That is, each of first and secondramps 18 and 20 may be a wedge having an incline extending along a planedefined by longitudinal axis 200 (i.e., may be inclined along thelongitudinal axis 200), while also being a wedge having an inclineextending along a plane defined a lateral axis 202 (i.e., may beinclined along the lateral axis 202). The inclination of first andsecond ramps 18 and 20 (and their associated mating features) along thelongitudinal axis 200 of expandable fusion device 10 may allow for theexpansion/compression of endplates 14 and 16 as first and second ramps18 and 20 translate with respect to one another along the longitudinalaxis 200. The inclination of first and second ramps 18 and 20 along thelateral axis 202 of expandable fusion device 10 may accommodate theuneven lengths of first and second sides 44, 45 of endplates 14, 16.

A method of installing the expandable fusion device 10 of FIG. 1 is nowdiscussed in accordance with one embodiment of the present disclosure.Prior to insertion of the expandable fusion device 10, theintervertebral space may be prepared. In one method of installation, adiscectomy may be performed where the intervertebral disc, in itsentirety, may be removed. Alternatively, only a portion of theintervertebral disc can be removed. The endplates of the adjacentvertebral bodies 2, 3 may be then scraped to create an exposed endsurface for facilitating bone growth across the intervertebral space.One or more introduction sheaths then. can be inserted into the discspace. The expandable fusion device 10 can then be introduced into theintervertebral space down an insertion sheath and seated in anappropriate position in the intervertebral disc space.

After the expandable fusion device 10 has been inserted into theappropriate position in the intervertebral disc space, the expandablefusion device 10 can then be transitioned from the collapsedconfiguration to the expanded configuration. To expand the expandablefusion device 10, the second ramp 20 may be moved toward the first ramp18. As the first and second ramps 18 and 20 move toward one another, therespective mating features of first and second ramps 18 and 20 may pushagainst corresponding mating features disposed on endplates 14 and 16 tomove expandable fusion device 10 into the expanded configuration. Insome embodiments, one or more of endplates 14, 16, and first and secondramps 18, 20 may include locking features for securing expandable fusiondevice 10 in the expanded configuration.

In the event the expandable fusion device 10 needs to be repositioned orrevised after being installed and expanded, the expandable fusion device10 can be contracted back to the collapsed configuration, repositioned,and expanded again once the desired positioning is achieved. To contractthe expandable fusion device 10, the first ramp 18 is moved away fromthe second ramp 20 via the actuating mechanism 300.

Actuating mechanism 300 may include any suitable actuating mechanismconfigured to translate first and second ramps 18 and 20 toward and awayfrom each other along the longitudinal axis 200. Referring to FIGS. 4and 7, actuating mechanism 300 may include a threaded member 302 (e.g.,a screw) that, when rotated in a first direction, directs first andsecond ramps 18 and 20 toward each other, moving expandable fusiondevice 10 from the collapsed configuration to the expandedconfiguration. When threaded member 202 is rotated in a second directionthat is opposite to the first direction, first and second ramps 18 and20 may be moved away from each other, causing expandable fusion device10 to move back toward the collapsed configuration. In one embodiment,threaded member 302 may be partially disposed through bore 515 of firstramp 18, and may further extend through bore 515 as expandable fusiondevice 10 is moved from the collapsed configuration to the expandedconfiguration. In this embodiment, threaded member 302 may push secondramp 20 toward first ramp 18, and may move coextensively with secondramp 20 during the transition of expandable fusion device 10 from thecollapsed configuration to the expanded configuration, and from theexpanded configuration to the collapsed configuration.

In an alternative embodiment shown in FIG. 19, threaded member 302 maybe at least partially disposed within bore 515 in the collapsedconfiguration. However, to transition from the collapsed configurationto the expanded configuration, threaded member 302 may be actuatedthrough second ramp 20. Unlike the embodiment shown in FIGS. 4 and 7, inthe embodiment of FIG. 19, threaded member 302 may pull first ramp 18toward second ramp 20, and may move coextensively with first ramp 18during the transition of expandable fusion device 10 from the collapsedconfiguration to the expanded configuration, and from the expandedconfiguration to the collapsed configuration. Any other suitableactuating mechanism may utilized, such as, e.g., sliders, pushers,ratchets, or the like.

In some embodiments, threaded member 302 may be rotated directly toactuate the actuating mechanism 300. In some embodiments, an inserter(not shown) may be configured to thread into or be otherwise coupled tothreaded member 302. In such embodiments, the inserter may be actuatedby suitable mechanisms (e.g., tools, ratchets, or the like) to rotatethreaded member 302 and adjust the relative position of the first andsecond ramps 18 and 20.

In some embodiments, only one of bores 366 and 418 may be threaded, suchthat expandable fusion device 10 may be actuated by linear movement ofactuating mechanism 300. For example, in one embodiment, bore 366 may bethreaded while bore 418 may not be threaded. in such an embodiment,threaded member 302 may be threaded into bore 366, and may be slidablethrough bore 418. After threaded member 302 is threaded through bore366, threaded member 302 can be selectively pushed through bore 418 tomove expandable fusion device 10 from the collapsed configuration to theexpanded configuration (e.g., by moving first ramp 18 and second ramp 20closer to one another). Additionally, threaded member 302 may be pulledin the opposite direction to move expandable fusion device 10 from thecollapsed configuration to the expanded configuration (e.g., by movingfirst ramp 18 and second ramp 20 away from one another). In thisembodiment, second ramp 20 may be pushed toward first ramp 18 to moveexpandable fusion device 10 from the collapsed configuration to theexpanded configuration.

In an alternative embodiment, bore 418 may be threaded and bore 366 maynot be threaded. In such an embodiment, threaded member 302 may bedisposed through bore 366 and threaded into bore 418 (e.g., referring toFIG. 1.9). Threaded member 302 may be pulled linearly to move expandablefusion device 10 from the collapsed configuration to the expandedconfiguration (e.g., by moving first ramp 18 and second ramp 20 closerto one another). Additionally, threaded member 302 may be pushed to moveexpandable fusion device 10 from the expanded configuration back to thecollapsed configuration (e.g., by moving first ramp 18 and second ramp20 away from. one another). In this embodiment, first ramp 18 may bepulled toward. second ramp 20 to move expandable fusion device 10 fromthe collapsed configuration to the expanded configuration.

In one embodiment, a locking member (e.g., a. screw not shown) may bedisposed separately of expandable fusion device 10 during the transitionbetween the collapsed and expanded configurations. Once the finalposition is achieved (e.g., the expanded configuration of expandablefusion device 10), the locking member may be advanced to lock expandablefusion device 10 into a desired configuration. In some embodiments, thelocking member may be integral with expandable fusion device 10, or maybe alternatively introduced after expansion. In some embodiments, thelocking member may be captured within the expandable fusion device 10 sothat it is not lost. In some embodiments, peening the tip of the lockingmember may prevent the locking member from becoming lost.

Once expandable fusion device 10 has been moved to the expandedconfiguration and locked via the locking member, bores 366 and 418,previously used to expand the expandable fusion device 10 via actuatingmechanism 300 may be utilized to pack graft or other bone growthinducing substances into expandable fusion device 10. That is, bores 366and 418 may he utilized to pack graft into the expandable fusion device10 to fill any potential gaps that formed during expansion of expandablefusion device 10.

With reference to FIGS. 20-24, an embodiment of expandable fusion device100 is shown. In an exemplary embodiment, the expandable fusion device100 may include a first endplate 114, a second endplate 116, a firstramp 118, and a second ramp 120. The first and/or second endplates 114,116 of the expandable fusion device 100 may include one or more openings126 to accommodate bone growth and/or bone growth materials.

The first endplate 114 includes an outer surface 140 configured toengage an adjacent vertebral body and an inner surface 142 configured tomate with at least a portion of the first and second ramps 118, 120. Thesecond endplate 116 includes an outer surface 145 configured to engagean adjacent vertebral body and an inner surface 144 configured to matewith at least a portion of the first and second ramps 118, 120. Thefirst ramp 118 includes an upper portion 128, which is sized to receiveat least a portion of the first endplate 114, and a lower portion 129,which is sized to receive at least a portion of the second endplate 116.The second ramp 120 may be disposed adjacent to the first ramp 118. Thesecond ramp 120 includes an upper portion 122, which is sized to contactat least a portion of the first endplate 114, and a lower portion 124,which is sized to contact at least a portion of the second endplate 116.The first and/or second ramps 118, 120 may include any of the matingfeatures described herein.

The first ramp 118 may include one or more bores 162, 164. The secondramp 120 may include a bore 166 adjacent bore 168. The bore 166 may beconfigured to receive an actuating mechanism 300 therethrough, and maybe aligned with the bore 164 in the first ramp 118. The bores 164, 166may be threaded, such that expandable fusion device 100 may be actuatedby linear movement of the actuating mechanism 300. The actuatingmechanism 300 may include a threaded member 302 as described above. Theactuating mechanism may also include one or more snap rings 134 and/orwashers 136. The snap rings 134 and washers 136 may be formed from anysuitable material, such as titanium, PEEK, or the like. After threadedmember 302 is threaded through bore 166, threaded member 302 can heselectively threaded through bore 164 to move the expandable fusiondevice 100 from the collapsed configuration to the expandedconfiguration (e.g., by moving first ramp 118 and second ramp 120 closerto one another).

Accordingly, expandable fusion device 100 may be movable between acollapsed configuration and an expanded configuration as describedherein. After the expandable fusion device 100 has been inserted intothe appropriate position in the intervertebral disc space, theexpandable fusion device 100 can then be transitioned from the collapsedconfiguration to the expanded configuration. To expand the expandablefusion device 100, the second ramp 120 may be moved toward the firstramp 118. As the first and second ramps 118 and 120 move toward oneanother, the respective mating features of first and second ramps 118and 120 may push against corresponding mating features disposed onendplates 114 and 116 to move the expandable fusion device 100 into theexpanded configuration. Thus, the expandable fusion device 100 is ableto reciprocally move between the collapsed and expanded configurations.

Depending on the expansion profile desired, symmetrical or asymmetricalexpansion of the device 100 may be required. Even if symmetricalexpansion is preferred, however, expandable implants that utilize rampsfor expansion may be subject to inconsistent expansion rates. Forexample, depending on the slope of the ramp interface or shape of themating features, the endplates 114, 116 may expand at a faster rate atthe back of the implant as opposed to the front of the implant. This isshown, for example, in FIG. 22 where the arm depict the relative ratesof expansion. By making the front ramp angles different from the backangles, the asymmetrical expansion issue ay be alleviated. For example,increasing the front ramp angles and decreasing the back ramp anglesensures that the endplates 114, 116 expand symmetrically.

The front and back ramp angles may be the same or different. As shown inFIGS. 23 and 24, an angle ε is provided for the front ramp angles (e.g.,the angle(s) on the mating features of the first ramp 118), and an angleδ is provided for the back ramp angles (e.g., the angle(s) on the matingfeature of the second ramp 120). These angles ε, δ are measured from thevertical axis μ. The angle ε may be provided on the mating surfaces forthe first ramp 118, the first endplate 114, and/or the second endplate116, respectively. The angle δ may be provided on the mating surfacesfor the second ramp 120, the first endplate 114, and/or the secondendplate 116, respectively. The angle ε is preferably larger than theangle δ, for example, at a ratio of about 4:1. The angle ε may rangefrom about 50-70°, 55-65°, 57-63°, 58-62°, or 59-61°. In a preferredembodiment, angle ε is 60°. The angle δ may range from about 5-25°,10-20°, 12-18°, 13-17°, 14-16°. In a preferred embodiment, angle δ is15°. Increasing the angle ε and decreasing the angle δ in this mannerensures that the endplates 114, 116 expand symmetrically. By expandingsymmetrically, the endplates 114, 116 are able to contact the vertebralbody endplates appropriately and maintain anatomical balance in situ.Although a symmetrical expansion is described, an asymmetrical expansionmay also be contemplated. The angles ε, δ may be changed or adjusted toprovide for asymmetrical expansion of the endplates 114, 116.

With reference to FIGS. 25 and 26, an embodiment of a first, front ramp218 is shown, which is suitable for use with any of the expandablefusion devices described herein. The first ramp 218 may have a first end270 on an insertion end of the device, a second end 272 configured tomate with the second ramp 20, 120, a first side portion 274, and asecond side portion 276 on the opposing side of the first ramp 218. Thefirst ramp 218 may extend generally from a first side 222 (e.g., aposterior side) to a second side 224 (e.g., an anterior side). The firstramp 218 may be generally wedge shaped, and may have a height thatincreases from the first side 222 toward the second side 224. The firstramp 218 may further include an upper portion 228, which is sized toreceive at least a portion of the first endplate 14, 114, and a lowerportion 229, which is sized to receive at least a portion of the secondendplate 16, 116. As discussed above, the second end 272 of the firstramp 218 may include bores 418, 515. In some embodiments, the bore 418may be configured to receive the threaded member 302 of the actuatingmechanism 300. The adjacent bore 515 may serve as an access port toallow graft material to be delivered through the first ramp 218 prior toinsertion or in situ.

The first ramp 218 may have a curvature or pitch on at least one rampsurface or mating feature. For example, the first end 270 may have acurved ramp surface 271. The second or anterior side 224 may have ahigher ramp angle than the first or posterior side 222 or vice versa.One or more portions of the first ramp 218 including one or more of theramp surfaces or mating features may include a continuously changingramp angle. The continuous linear change of the implant's angle (e.g.,lordotic angle) may be contingent on a continuously changing ramp angle.This results in a curvature of the ramp surface which can be defined byangular change per distance away from the pivot axis π. This value isthe pitch of the implant ramp surfaces, and is responsible for varyingthe rate of angular change the implant is able to achieve. A largerpitch value correlates to a higher ramp angle at the anterior ramp edgein relation to the angle at the posterior ramp edge for an implant offixed width. The mating features, ramp angles, type of angle change,lordotic angle, rate of expansion, and the like may be configured asdescribed herein to provide for optimal design and functionality of thedevice.

Any aspect set forth in any embodiment may be used with any otherembodiment set forth herein. Every device and apparatus set forth hereinmay be used in a suitable medical procedure, such as, e.g., a vertebraldisc replacement procedure, and may be advanced through any suitablebody lumen and body cavity.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the disclosed systems andprocesses without departing from the scope of the disclosure. Otherembodiments of the disclosure will be apparent to those skilled in theart from consideration of the specification and practice of thedisclosure disclosed herein. It is intended that the specification andexamples be considered as exemplary only. The following disclosureidentifies some other exemplary embodiments.

We claim:
 1. An expandable fusion device comprising: a first endplateand a second endplate, wherein the first and second endplates eachinclude at least one mating feature; a first ramp configured to matewith both the first and second endplates, wherein the first rampincludes a mating feature having a first angle relative to a verticalaxis, wherein the at least one mating feature of the first endplate orsecond endplate is slidable with respect to the corresponding matingfeature disposed on the first ramp; and a second ramp configured to matewith both the first and second endplates, wherein the second rampincludes a mating feature having a second angle relative to the verticalaxis, wherein the first angle is different from the second angle.
 2. Theexpandable fusion device of claim 1, wherein the first angle is greaterthan the second angle.
 3. The expandable fusion device of claim 1,wherein the first angle is about 50-70°.
 4. The expandable fusion deviceof claim 1, wherein the first angle is about 60°.
 5. The expandablefusion device of claim 1, wherein the second angle is about 5-25°. 6.The expandable fusion device of claim 1, wherein the second angle isabout 15°.
 7. The expandable fusion device of claim 1, wherein the firstand second ramps are configured to provide for symmetrical expansion ofthe first and second endplates.
 8. The expandable fusion device of claim1, wherein at east a portion of the first ramp includes a curved rampsurface.
 9. The expandable fusion device of claim 1, wherein at least aportion of the first ramp has a continuously changing ramp angle. 10.The expandable fusion device of claim 1, wherein each of the first andsecond endplates have an inner surface configured to mate with the firstramp, wherein the inner surface of each of the first and secondendplates are shaped as a concave curve, the concave curve being formedabout a longitudinal axis of the expandable fusion device.
 11. Theexpandable fusion device of claim 1, wherein the expandable fusiondevice is movable between a collapsed configuration and an expandedconfiguration.
 12. The expandable fusion device of claim 11, wherein thefirst ramp is coupled to the second ramp by an actuating mechanism, andthe expandable fusion device is configured to transition from thecollapsed configuration to the expanded configuration via actuation ofthe actuating mechanism to move the second ramp and the first ramptoward one another.
 13. The expandable fusion device of claim 11,wherein, in the expanded configuration, the expandable fusion device isa wedge having an incline extending along the lateral axis of theexpandable fusion device.
 14. The expandable fusion device of claim 1,wherein the first and second endplates each have an outer surfaceconfigured to contact a respective vertebral body, wherein each outersurface of the first and second endplates has one or more of teeth,ridges, friction increasing elements, keels, or gripping or purchasingprojections.
 15. An expandable fusion device, comprising: a firstendplate and a second endplate, both the first and second endplatesextending from a first side of the expandable fusion device to a secondside of the expandable fusion device; a first ramp and a second ramp,both the first ramp and the second ramp being configured to mate withboth the first and second endplates, and both the first ramp and thesecond ramp extending from the first side of the expandable fusiondevice to the second side of the expandable fusion device, wherein atleast one of the first and second sides of the expandable fusion devicepivotally expand about a pivot point, and wherein the first and secondramps are configured to provide for symmetrical expansion of the firstand second endplates.
 16. The expandable fusion device of claim 15,wherein the first ramp includes a mating feature having a 60° anglerelative to a vertical axis and the second ramp includes a matingfeature having a 15° angle relative to the vertical axis.
 17. Theexpandable fusion device of claim 15, wherein both of the first andsecond sides of the expandable fusion device pivotally expand about thesame pivot point.
 18. The expandable fusion device of claim 17, whereinthe same pivot point is a point disposed outside of the expandablefusion device.
 19. The expandable fusion device of claim 15, herein thepivot point is disposed along the first side or between the first andsecond sides of the expandable fusion device.
 20. The expandable fusiondevice of claim 15, wherein the expandable fusion device is movablebetween a collapsed configuration and an expanded configuration, and theexpandable fusion device has a continuous linear angular rate of changewhen moving between the collapsed configuration and the expandedconfiguration.